Food Webs

The feeding relationships Huia had with other animals were very simple. They were omnivorous, eating insects, larvae, spiders and berries. They were not eaten by anything else until the arrival of humans; then rats ate their chicks and eggs, while cats, dogs and stoats ate the birds themselves.

Some Huia Food Chains

These food chains show Huia as 1st Order Carnivores (2nd Order Consumers), 2nd Order Carnivores (3rd Order Consumers) and as Herbivores (1st Order Consumers):

Before Humans

As Huia are now extinct, it is difficult to know for certain which species were the main competitors. The beak of Huia was specialised to limit competition within the species, so it is more likely that they avoided competition with other species too. Kereru, saddlebacks, Kiwi and other birds were likely competitors, but also subject to the same introduced predators upon the arrival of humans; their numbers would have decreased in a similar fashion to the Huia's.

The New Zealand forest ecosystems were well-balanced without the presence of humans, leading to Huia (and other species) to have very specialised adaptations and a lack of variation within each population. As such, the introduction of new species and the clearing of forests (and the food sources they harboured), had a devastating impact on the Huia populations.

After Humans - the Road to Extinction

Humans introduced a lot of species which predated upon Huia (and other birds and reptiles). Humans also cleared forests to make the land available for agriculture. Many of the old, large trees in New Zealand forests had beautiful timber, ideal for building and furniture-making. Humans reduced the size of the Huia's habitat, introduced new threats, and hunted them for food and for its ornate beak and tail feathers.

The changes to this food web played a large part in the extinction of Huia. Chicks were eaten by the introduced predators, rats competed for some of the Huia's food source, and the availability of wood detritus for insects and Huhu grubs also limited its food supply.

The Huia was in big trouble, particularly as it was reportedly unable to adapt well enough to survive in alternate habitats. However, its habitat was never completely removed, so this alone should not have led to its extinction. The food web above shows the likely primary reason for Huia's extinction - new predators that it had limited ability to evade. Many New Zealand species were made extinct due to the introduction of rats, dogs, cats and stoats. The introduction of possums which compete for the birds' food source has also had a devastating impact. Kiwi, Kokako and Kakapo are examples of other New Zealand birds which were driven to the brink of extinction in a similar way; fortunately, conservation efforts were not too late to save these species...for now.

Community

Range

There are conflicting reports about how widespread Huia were in New Zealand. Some reports say that they were only found in the mountainous regions of the North Island (Te Ika-a-Māui), while there are also reports of Huia being sited in the Marlborough and Nelson regions of the South Island (Te Wai Pounamu).

http://www.daandehn.com/images/new-zealand-map.jpg

Either way, it is known that their range reduced upon the arrival of the first humans (Māori), and dramatically upon the formal European settlement of New Zealand in 1840. The last official siting of Huia in the wild was in 1907, in the Tararua Ranges.

http://www.fmc.org.nz/wp-content/uploads/Images/Tararuas600px.jpg

Habitat

Huia lived in tall forests with dense understory (the level immediately below the canopy).

The main tree species in these forests were Mataī, Rimu, Kahikatea, Northern Rātā, Maire, Hinau, Totara, Rewarewa, Mahoe, and Taraire. Many of these trees would have provided both shelter and food for Huia. Huhu grubs, Weta and spiders would be found in the decaying wood of trees. The forest was also a home to many insect varieties. Additionally, some of these trees produce berries, another food source for many bird species including Huia.

Mataī

Rimu

Unfortunately for the forest-dwellers, the wood from these trees made for excellent furniture and housing. The forests were also very dense, so needed to be cleared to make the land available for human use.

Huia were never found in land cleared for farming or burnt forest. The deforestation of New Zealand's forests by both Māori and European settlers played a large part in Huia becoming endangered, then extinct.

Environment

The mountainous regions of New Zealand's North Island are described as temperate, but can be subject to snow and strong winds. Temperatures seldom exceed 30°C and rainfall is relatively uniform throughout the year (although the winter months are cooler and wetter). Water availability is rarely a limiting factor in these regions of New Zealand.

The size of the trees found in New Zealand forests protect the forest floor and understory from many of the more adverse weather conditions. However, they also limit the availability of light for many plants on the forest floor; plants below the canopy tend to have large leaves to make the most f the light that does filter through. The strong winds would cause branches to break, giving a food source for decomposers in the habitat.

Relationships

The New Zealand forest relies upon frugivorous birds such as Huia for seed dispersal. Huia would only be able to eat fruits smaller than 1cm in diameter, so only involved in the dispersal of Hinau, Kahakitea and some indigenous Coprosma species. It would have been in competition with other birds, particularly the NZ Wood Pigeon (Kereru). Decline in numbers of these birds (along with deforestation by humans) contributed to the decline of New Zealand forest. Huia were possibly also in competition with the NZ bat (pekapeka), which eats the berries of many indigenous plants.

Huia would also have competed with many other bird species for insects, spiders and larvae found in decomposing logs. Kiwi were a very successful forager, but were nocturnal which would limit the direct competition between these species.

The extinction of Huia also led to the extinction of a parasitic louse, Rallicola extinctus, as it lost its host. It did not have an alternate host.

Huia had no natural predators, but the arrival of the Māori saw the introduction of the Polynesian rat (kiore) which would predate upon Huia chicks. Dogs (kurī) were also introduced by the Māori and it is likely they predated upon adult Huia. Europeans brought many more predators, including cats and stoats.

While the Māori did hunt Huia for their ornate feathers and their beaks, there are varied reports about whether they made good eating or not. When the Māori noticed Huia numbers declining, they would declare them sacred (tapu), banning the hunting/killing of them. Māori chiefs would ask European settlers to not hunt Huia in these times. Sadly, early European settlers did not have the same conservation focus as the Māori.

Adaptations

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The most noticeable adaptations of the Huia are:

1. The characteristic beak of the female.
2. The difference between the beak shape of the male and female.
3. Dark plumage.
4. The bright orange wattle.
5. The long tail feathers with white tips.

There are also some other important adaptations which are not so obvious, which will be discussed here.

Beaks and Feeding

The difference between the beaks in Huia is called sexual dimorphism. It is not actually all an uncommon structural adaptation (riflemen, sicklbills and even kiwi have this) but is probably most pronounced in Huia.

The reason for sexual dimporhism in beak shape and size is to reduce competition within the same species (and therefore, within the same population). Interestingly, both sexes had very similar diets, but the different beaks allowed them to find/access their food from different places.

Diet/Feeding

Huia were omnivores and considered to be experts at feeding on Huhu beetle larvae (huhu grubs), Prionoplus reticularis. They also ate a wide range of other insect larvae, as well as Weta, spiders and berries.

Huhu grubs - yum!

Accounts from early settlers describe the feeding of Huia - they would take their food to a perch, their food in their claws, strip off anything hard (like an exoskeleton), throw it into the air and catch it in their beak.

Male

• approximately 60mm long
• only slightly curved
• robust (like a woodpecker)

The male used its bill to chisel into the outer layers of decaying or live wood. To do this it had to be robust and relatively straight.

Female

• approximately 100mm long
• very pronounced curve
• fine (like a hummingbird)

The shape of the female's bill allowed her to probe areas inaccessible to the male, such as the burrows of insect larvae in living wood.

Bright Orange Wattle

The wattle either side of the beak is characteristic of the Callaeidae Family, which includes Huia, Kokako and saddleback (Tieke). The actual purpose of the wattle is a bit of a mystery, but in turkeys it is used to select a mate. It is likely this was its purpose in Huia as well.

Plumage

The feathers of Huia were black with a green tinge. This would have helped Huia be well camouflaged in the dark New Zealand rain forests, which had very tall trees limiting the amount of light getting below the canopy. With no natural predators (until the arrival of humans), this was probably more important for catching insects.

The white tip on the tail feathers was a unique feature (for New Zealand birds) of Huia. This made them a desirable commodity for both Maori and European settlers. Sadly, to collect these feathers, the birds had to be killed. The purpose of the white tip is unknown, but it is likely that it also helped break up the shape of Huia. Huia were not strong fliers (like a lot of NZ birds), so this breaking up of their shape may have helped in catching insects.

Its large tail was used (in conjunction with its short wings and strong legs) to move in long leaps and bounds through the canopy or along the forest floor. It was also used to help it balance when holding onto tree trunks (vertically. like a woodpecker). It did this by spreading the tail out.

Mating

Huia mated for life; that is, they had only one partner for mating. This is usually a disadvantage, but the lack of predators and small range of Huia meant that this was actually an advantage - they did not need to waste energy competing for mates every year. However, the arrival of humans along with their introduced predators (rats, dogs etc) led to this adaptation being a huge disadvantage for Huia populations.

Breeding and nesting usually occurred during early summer, when there was plenty of dry foliage and twigs for nest-building. The nest was built either in a hollow tree or in a mass of dense vegetation. Nesting took place in November. The clutch size was two to four eggs, which were greyish with purple and brown speckles and measured 45mm by 30mm; the colour of these eggs would help camouflage them in their nests. Most Huia nests were found near the summits of mountain ranges.

Behaviour

Huia are described as being quiet, social birds which were not afraid of humans. This made them easy to capture by hand. They were usually found in breeding pairs, but sometimes also in social groups of four (presumably two breeding pairs).

Huia had a loud distress call and were named after the sound of this call. However, it has been described as sounding more like "who-are-you" by some.

Their social, trusting behaviour is typical of animals with no natural predators, which makes it interesting that they had a distress call. It may be inferred that this distress call evolved upon the arrival of humans, but this can never be confirmed.

Summary

Huia probably developed these structural, behavioural and physiological adaptations over time due to the lack of natural predators, and to limit competition (particularly intraspecific). The fact that Huia were widespread throughout New Zealand until the arrival of Maori suggests that it could not adapt quickly enough to the introduction of predators, to human exploitation and to the introduction of competitors.

References

Thank you to these websites for the information found in this blog:
http://www.avianweb.com/huia.html
http://www.nzbirds.com/birds/huia.html
http://www.kcc.org.nz/huia
http://en.wikipedia.org/wiki/Huia
http://christchurchcitylibraries.com/Kids/NZBirdsAnimals/Huia/
http://collections.tepapa.govt.nz/theme.aspx?irn=1339
http://www.shropshire.gov.uk/legacy/llmrc.nsf/open-coll/Huia%20bird
http://www.teara.govt.nz/en/extinctions/6/3/1

http://socyberty.com/society/the-huhu-grub-a-new-zealand-maori-delicacy/

http://www.arkive.org/huia/heteralocha-acutirostris/